PROJECT SUMMARY Severe alcoholic hepatitis (SAH) is the most severe form of the alcoholic liver diseases (ALD). Chronic alcohol abuse is associated with increased susceptibility to pneumonia, infections (e.g., HIV, HCV, and Tuberculosis), and with chronic inflammation. Studies in the past thirty years in both humans and animal models revealed that ALD is likely caused by impact of alcohol abuse on adaptive immune system. Chronic alcohol abuse was found to reduce the number of B cells, decrease antigen-specific antibody responses, and increase the production of autoantibodies against liver autoantigens and byproducts of oxidative damage. Moreover, increased levels of immunoglobulin of IgG, IgA, and IgE isotypes and production of autoantibodies against liver antigens have been observed in patients with SAH. Therefore, we hypothesize that generation of autoantibodies in patients with SAH contributes to liver damage. To fully test this hypothesis, the identification of those antigens recognized by antibodies deposited in SAH livers is a crucial stepping-stone towards understanding the etiology of the diseases. In addition, it is likely that some of these antibodies are created from cross-reacting antibodies directed against bacteria in the gut. The goal of this proposal is to determine the origins of these SAH-specific antibodies in patients with SAH and characterize their function and contribution to liver damage. We will take full advantage of the biospecimens collected from the explanted livers of patients with SAH, as well as donor livers and livers diagnosed for other liver diseases, and employ the cutting-edge protein microarray technology to achieve four Specific Aims: 1) Identify autoantigens that are specifically recognized by antibodies extracted from explanted livers or blood of the patients with SAH; 2) Profile antibody signatures to bacterial antigens in patients with SAH; 3) Characterize functions of the antibodies extracted from SAH livers using a cell-based model; and 4) Examine whether alcohol abuse-induced autoantibodies cause liver allograft injury in alcohol relapse patients after liver transplantation. We believe that of this project will allow us to identify novel therapeutic targets and develop novel therapy for intervention and prevention of SAH.